LD1117AS18TR from STMicroelectronics, in a SOT-223-3. Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin	Name	Type	Function
1	ADJ/GND	power_in	Ground reference pin for the fixed-output versions (LD1117AS18 uses this pin as GND). On the adjustable variant this same pin is the ADJ feedback input (VREF = 1.25 V to the external divider). Connect to system ground for the LD1117AS18TR (1.8 V fixed).
2	VOUT	power_out	Regulated 1.8 V output. Sources up to 1 A (1.2 A typical current limit). Requires a minimum 10 µF output capacitor to GND for loop stability. The SOT-223 tab is internally connected to this pin.
3	VIN	power_in	Unregulated DC input supply. Operating input voltage up to 10 V (absolute max 15 V). Dropout ≤1.15 V typ at 1 A, so VIN must be ≥ VOUT + VDROPOUT. A 100 nF input capacitor is recommended close to the pin.
TAB	VOUT	power_out	SOT-223 thermal tab, internally shorted to the VOUT pin (pin 2). Provides the primary heat-sinking path (RthJC = 15 °C/W, RthJA = 110 °C/W). Solder to a copper pour tied to VOUT to improve thermal performance.

Key specifications

Parameter	Value
Manufacturer	STMicroelectronics
Package	SOT-223-3
Category	PMIC
Pins	4

Ordering variants

Same part, different packaging or reel option.

LD1117AS18TR
LD1117ADT18TR
LD1117AV33

CAD (KiCad official)

Symbol: LD1117AS18TR
Footprint: Package_TO_SOT_SMD:SOT-223-3_TabPin2
3D model: SOT-223-3 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`ld1117as18tr.step`	64 KB	You want the bare part, or you mark your own boards.
`ld1117as18tr-etched.step`	1.8 MB	You want the part with `LD1117AS18TR` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 454 faces against 75 in the bare model. It survives export, section views, and rendering in any CAD tool, and it drops straight into KiCad or Fusion with no extra setup.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: STMicroelectronics datasheet (24 pp, sha256 5cf3aab5b1478366, retrieved 2026-08-17, tier: lcsc)
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF